Magneto caloric material (MCM)—i.e. a material that exhibits the magneto caloric effect—provides a potential alternative to fluid refrigerants used in e.g., heat pump applications. In general, the magnetic moments of a normal MCM will become more ordered under an increasing, externally applied magnetic field and cause the MCM to generate heat. Conversely, decreasing the externally applied magnetic field will allow the magnetic moments of the MCM to become more disordered and allow the MCM to absorb heat. Some MCM types exhibit the opposite behavior—i.e. generating heat when a magnetic field is removed and becoming cooler when placed into the magnetic field. This latter type can be referred to as inverse or para-magneto caloric material. Both normal and inverse MCM are referred to collectively herein as magneto caloric material or MCM. The theoretical cycle efficiency of a refrigeration cycle based on an MCM and the magnetic caloric effect can be significantly higher than for a comparable refrigeration cycle based on a fluid refrigerant.
Challenges exist to the practical and cost competitive use of an MCM, however. In addition to the development of suitable types of MCM, equipment that can attractively utilize an MCM is still needed. Some MCM-based devices use a regenerator having a construction where a heat transfer fluid flows between parallel plates constructed of MCM. Other regenerators may use beds of MCM particles through which the heat transfer fluid flows to exchange heat. The plate arrangement can provide for a low pressure drop in the flow of the heat transfer fluid through the regenerator but suffers from an overall low surface area for heat transfer. Regenerators using particle beds provide substantial surface area for heat transfer but also incur a substantial pressure drop in the flow of the heat transfer fluid.
Additionally, the ambient conditions under which the MCM-based regenerator may be applied can vary substantially. For example, for a refrigerator appliance placed in a garage or located in a non-air conditioned space, ambient temperatures can range from below freezing to over 90° F. Some types of MCM are capable of accepting and generating heat only within a much narrower temperature range (sometimes referred to as the Curie temperature range) than presented by such ambient conditions. Also, different MCM types may exhibit the magneto caloric effect more prominently at different temperatures.
Accordingly, a regenerating device that can address certain challenges including those identified above would be useful. Particularly, a regenerator that can provide improved pressure drop and surface area for the heat transfer fluid would be useful. A regenerator that can be equipped for use in a wide range of ambient temperature conditions would be also be beneficial. A heat pump or appliance using such a regenerator would also be useful.